Manipulating adsorbed hydrogen on lanthanum-modified CuO_x: Industrial-current-density CO₂ electroreduction to C₂₊ products or CH₄

The selective electrochemical CO₂ reduction reaction (CO₂RR) yields valuable C₂₊ and C₁ products, yet the influence of adsorbed hydrogen (*H) on product distribution remains inadequately understood. This study explores this effect by developing bimetallic copper-based electrocatalysts with varied lanthanum (La) doping ratios. The oxide-derived (OD)-La_0.10-CuO_x catalyst exhibits a Faradaic efficiency (FE) over 80% for C₂₊ products at 300 mA cm⁻², whereas OD-La_0.40-CuO_x achieves a 61.4% FE_CH4 at 400 mA cm⁻². Kinetic isotope experiments reveal distinct dependencies of the rate-determining steps on *H transfer for CO₂RR in OD-La_0.10-CuO_x and OD-La_0.40-CuO_x. In situ ATR-SEIRAS and DFT calculations demonstrate that the moderate H₂O dissociation capability of OD-La_0.10-CuO_x lowers the energy barrier for *CHO → *OCCHO conversion, thus increasing the FE_C2+. Conversely, OD-La_0.40-CuO_x, with its strong H₂O dissociation capability, favors *CHO → *CH₂O, thereby promoting CO₂RR-to-CH₄. These findings advance the understanding of the role of *H in CO₂ electroreduction at industrial current densities and present avenues for tailored CO₂RR products via doping engineering.